Field of the Invention
This invention relates generally to a device for detecting a displacement amount of a movable member, and particularly to a displacement amount detecting device which outputs pulse signals corresponding to such a displacement amount.
Description of the Prior Art
Heretofore, a displacement amount detecting device of a similar type has been known in which a displacement-phase transducer such as, for example, a resolver or a magnetic scale, is used to transduce a displacement amount of a movable member to a phase angle. The converted phase angle is then converted to pulses of the number corresponding thereto, and the number of the pulses which are converted during predetermined periods of time different from each other are successively compared so as to output an increment of the pulse number as a displacement amount of the movable member.
However, in this displacement amount detecting devices, there is necessitated a memory circuit for storing the number of pulses converted during the previous period of time and an arithmetic circuit for comparing the stored number of pulses with the number of pulses converted during the following period of time so as to output pulses of the number corresponding to the difference therebetween. In addition, a control circuit is necessitated to cause the memory circuit and the arithmetic circuit to so operate within a predetermined interval of time. As a result, this displacement amount detecting device is structurally complicated and is also expensive.